Regularity Analysis Of Key Safety Parameters Of Subway Foundation Pit Construction

With the rapid development of the urban economy and the urgent needs of people's life travel,the construction of the subway is based on the first-tier cities in China,and it has been expanded to a large extent;As an important temporary project in Metro construction,the regularity study of key safety parameters in metro foundation pit construction is of great significance for guiding the excavation of foundation pit and preventing safety accidents.This paper takes the 1# foundation pit engineering of the excavation section of the Gaotangqiao Station to the Juzhang Station of the first phase of the Ningbo Rail Transit Metro Line 3 as the research object,and uses the combination of theoretical knowledge and on-site monitoring data analysis to the subway pit.The key parameters of the construction are analyzed regularly.In order to study the variation law of the bottom of the pit and the support axial force,this paper uses the method of mathematical statistics analysis to analyze and sort out a large number of pit bottom uplift and support axial force monitoring data,and obtain the foundation uplift value and steel support of the subway foundation pit.The law of the uplift value of the foundation pit of the subway and the axial force of the steel support with time,excavation depth and temperature are obtained.According to the soil conditions in Ningbo,the research results are as follows:1?With the change of time,relative pit bottom bulge value increases with form of exponential function growth.The bottom of the pit is stable after 10~15d after the excavation of the foundation pit;With the change of the excavation depth,the limit value of relative pit bottom bulge increases with form of exponential function growth.Within the excavation depth range of 20~47m,the relative ridge limit value is stable;With the change of relative temperature,the relative bulge value varies linearly.For every 1 ? change in ambient temperature,the value of the bottom of the pit will change by 0.55 mm;2?The axial force of section support varies linearly with the change of excavation depth;The relative axial force of the steel support is positively correlated with the relative temperature change.For every1 ? increase in steel support temperature,the support axial force increases by 24.5 kN;Comparing the calculation results of steel support axial forcegrowth under unit temperature increase with the measured results,the analysis found that the calculation result is larger than the measured results.